Ultrafast Camera Records at Speed of Light

From the editors and reporters of Scientific American , this blog delivers commentary, opinion and analysis on the latest developments in science and technology and their influence on society and policy. From reasoned arguments and cultural critiques to personal and skeptical takes on interesting science news, you'll find a wide range of scientifically relevant insights here. Follow on Twitter @sciam.

Larry Greenemeier is the associate editor of technology for Scientific American, covering a variety of tech-related topics, including biotech, computers, military tech, nanotech and robots. Follow on Twitter @lggreenemeier.

Researchers at the Massachusetts Institute of Technology (M.I.T.) have developed an imaging system that can acquire visual data at a rate of one trillion exposures per second–fast enough to produce a slow-motion video of a burst of light traveling the length of a one-liter bottle, bouncing off the cap and reflecting back to the bottle’s bottom.

As Ramesh Raskar, an associate professor in M.I.T.’s Media Lab, explains in the video below, a high-speed camera can capture the image of a bullet mid-flight. The M.I.T. camera can capture the movement of photons, which travel about one million times faster than bullets.

The researchers use a titanium-sapphire laser as a pulsed light source and direct the beam using mirrors to a plastic bottle that helps illuminate the light. Their camera consists of an array of 500 sensors, each triggered at a trillionth-of-a-second delay, Media Lab postdoctoral associate Andreas Velten says in the video. The images are combined to get a complete movie of photon movement.

The researchers, part of the Media Lab’s Camera Culture group, expect that such a camera could have practical applications in medical imaging, scientific and industrial research and possibly even consumer photography.

About the Author: Larry Greenemeier is the associate editor of technology for Scientific American, covering a variety of tech-related topics, including biotech, computers, military tech, nanotech and robots. Follow on Twitter @lggreenemeier.

19 Comments

I am confused by the video title stating the camera is taking one trillion frames per second? Shouldn’t the article more correctly state one trillion horizontal pixels per second? As Dr. Velten points out at approx. 1:33, a very slowly vertical scanning mirror is used to scan the field of interest. One frame, by definition, consists of a 2D array of pixels, thus the video title should read as 1 trillion single pixel exposures per second?

If you are looking to scan a biological tissue medium such as a finger, why not pulse the laser with a one microsecond to a one nanosecond width pulse, and reduce the intensity of the optical power?

@lamorpa, there’s nothing fishy about moving a gaze so fast. While looking at the stars, you can look from Jupiter to Saturn in a second, even though it takes many minutes for light to go between the two.
I would agree that the editors are spinning the article with inaccurate titles and phrases with the intent to snag readers looking for articles about the more-interesting quantum action at a distance in recent news. They also seem to misinterpret a pack of photons (pulse) as a single photon.
Makes me distrust anything coming from Larry Greenemeier or Sci Am editors.

This makes for tricky terminology. They have not captured video of a single light pulse moving through a bottle. They have made a composite video made of many different but identical light pulses that shows how each light pulse moves through the bottle.

Its definitely cool and important, although those guys need to be careful not to misrepresent the results.

On the video Professor Raskar states, “We have built a virtual slow motion camera where we can see photons or light particles moving through space.” As exciting as it sounds, I respectfully submit that one cannot “see,” “image” or “photograph” light from any angle but the incident, i.e., light is not “visible” except when it impacts a sensor.

The body of the article mentions that the bottle “helps illuminate the light,” but I would suggest that it more accurately “scatters” (as worded in the photo’s caption) the light, which permits stray rays to be incident to the camera’s lens and thus refracted, impinged on the sensor arrays and imaged.

It might be remotely possible to image a photon (or stacked photon pack) by reflecting smaller particles off it, but in this study, that is not the case.

Such a high speed camera is extremely useful and an outstanding accomplishment, but I believe in the excitement of discovery they may have overstated its capability. When Dr. Velton explained that “because all of our pulses look the same,” I surmised that what is imaged are overlapping laser pulses which could be phased or “clocked” by the camera to move in the opposite direction as well, and this would indicate they are not capturing the actual motion of light. But they have indeed synchronized with the period of the laser and this is commendable.

“A trillion exposures per second” would allow a per frame exposure of at most one trillionth of a second. The distance light travels in that time through a vacuum is 0.000299792458 meters, or around 0.3 millimeters, which would be the distance the laser travels in that time. The light band in the apple video sample appears to be in the range of a centimeter, so the exposure appears to be around thirty-three times longer, suggesting a range of 30 billion exposures per second.

Another aspect to this experiment is the phenomenon of “illumination banding” in still images captured by scanning digital cameras employing a cyclical light source such as 60-hz mercury vapor. Because this employs the cyclical laser illumination, so is such an effect be playing a role in this?

To me, the title says it all, and the article is a tad misleading. If the camera RECORDS at or faster than light, it simply means it can depict “something” in space during a time interval shorter than the time it would take for a photon to cross the space it occupies. We can already record time intervals far shorter than the equivalent light transit time, so this article seems to say an image can be produced as well. I would think we would therefore only see an image on a frame from just those photons recorded during that short time interval (a content ‘stream ensues if the subject is continually illuminated, after all, so photons would always be available to the detector). Over a stack of images, we would see (if that is the proper term) how light reflects from (illuminates) an object, in theory photon by photon, depending on how the illumination/reflection occurs and the number of pixels (detectors) are in the array. A neat trick; I’d really like to have someone recount practical use of this capability.

You bring up an interesting point in terms of transit time. Because light travels roughly 300mm/nanosecond, the time taken for the light band to return to the lens from the subject in the apple image would distort due to differing distances in the suggested picosecond timeframe. The apparent curvature of the light band is a result of the convex mirror which disperses the laser and not transit lag, but this is difficult to determine with certainty. A good proof would be to display the light band sweeping from one side on a clear plane nearly parallel to the lens axis to demonstrate transit lag distortion.

Moreover, suppose there is very misty/smoky environment and i’m recording a video of a laser beam pointed towards me. Laser is switched on in the meanwhile say at time=T. Say, light takes time=t to reach my camera. Nw, as they say they can see light in slow motion, i can see my recording at time=t+t/2 when light is mid-way. But how did my camera know that there was a signal sent even before light could reach it. THIS DEFIES THEORY OF RELATIVITY AND ALL OF THIS IS NONSENSE

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